Millions
of years ago, a few spiders abandoned the kind of round webs that the
word “spiderweb” calls to mind and started to focus on a new strategy.
Before, they would wait for prey to become ensnared in their webs and
then walk out to retrieve it. Then they began building horizontal nets
to use as a fishing platform. Now their modern descendants, the cobweb
spiders, dangle sticky threads below, wait until insects walk by and get
snagged, and reel their unlucky victims in.

In 2008, the researcherHilton Japyassúprompted
12 species of orb spiders collected from all over Brazil to go through
this transition again. He waited until the spiders wove an ordinary web.
Then he snipped its threads so that the silk drooped to where crickets
wandered below. When a cricket got hooked, not all the orb spiders could
fully pull it up, as a cobweb spider does. But some could, and all at
least began to reel it in with their two front legs.

Their ability to recapitulate the ancient spiders’ innovation got
Japyassú, a biologist at the Federal University of Bahia in Brazil,
thinking. When the spider was confronted with a problem to solve that it
might not have seen before, how did it figure out what to do? “Where is
this information?” he said. “Where is it? Is it in her head, or does
this information emerge during the interaction with the altered web?”

In February, Japyassú and Kevin Laland, an evolutionary biologist at the University of Saint Andrews, proposed a bold answer to the question. They argued in a review paper, published in the journal Animal Cognition,
that a spider’s web is at least an adjustable part of its sensory
apparatus, and at most an extension of the spider’s cognitive system.

This would make the web a model example of extended cognition, an idea first proposed by the philosophers Andy Clark and David Chalmers in 1998 to apply to
human thought. In accounts of extended cognition, processes like
checking a grocery list or rearranging Scrabble tiles in a tray are
close enough to memory-retrieval or problem-solving tasks that happen
entirely inside the brain that proponents argue they are actually part
of a single, larger, “extended” mind.

Among philosophers of mind, that idea has racked up citations,
including supporters and critics. And by its very design, Japyassú’s
paper, which aims to export extended cognition as a testable idea to the
field of animal behavior, is already stirring up antibodies among
scientists. “I got the impression that it was being very careful to
check all the boxes for hot topics and controversial topics in animal
cognition,” said Alex Jordan, a collective behaviorial scientist at the Max Planck Institute in Konstanz, Germany (who nonetheless supports the idea).

While many disagree with the paper’s interpretations, the study
shouldn’t be confused for a piece of philosophy. Japyassú and Laland
propose ways to test their ideas in concrete experiments that involve
manipulating the spider’s web — tests that other researchers are excited
about. “We can break that machine; we can snap strands; we can reduce
the way that animal is able to perceive the system around it,” Jordan
said. “And that generates some very direct and testable hypotheses.”The Mindful Tentacle

The suggestion that some of a spider’s “thoughts” happen in its web
fits into a small but growing trend in discussions of animal cognition.
Many animals interact with the world in certain complicated ways that
don’t rely on their brains. In some cases, they don’t even use neurons.
“We have this romantic notion that big brains are good, but most animals
don’t work this way,” said Ken Cheng, who studies animal behavior and information processing at Macquarie University in Australia.

Parallel to the extended cognition that Japyassú sees in spiders,
researchers have been gathering examples from elsewhere in the animal
kingdom that seem to show a related concept, called embodied cognition:
where cognitive tasks sprawl outside of the brain and into the body.

Perhaps the prime example is another eight-legged invertebrate.
Octopuses are famously smart, but their central brain is only a small
part of their nervous systems. Two-thirds of the roughly 500 million
neurons in an octopus are found in its arms. That led Binyamin Hochnerof the Hebrew University of Jerusalem toconsider whether octopuses use embodied cognition to pass a piece of food held in their arms straight to their mouths.

For the octopus, with thousands of suckers studding symmetric arms,
each of which can bend at any point, building a central mental
representation of how to move seems like a computational nightmare. But
experiments show that the octopus doesn’t do that. “The brain doesn’t
have to know how to move this floppy arm,” Cheng said. Rather, the arm
knows how to move the arm.

Readings
of electric signals show that when a sucker finds a piece of food, it
sends a wave of muscle activation inward up the arm. At the same time,
the base of the arm sends another wave of clenched muscles outward, down
the arm. Where the two signals meet each other, the arm makes an elbow —
a joint in exactly the right place to reach the mouth.

Yet another related strategy, this one perhaps much more common and
less controversial, is that the sensory systems of many animals are
tuned in to the parts of the world that are relevant to their lives.
Bees, for example, use ultraviolet vision to find flowers that have also
evolved ultraviolet markings. That avoids the need to take in lots of
data and parse it later. “If you do not have those receptors, that part
of the world simply doesn’t exist,” saidWilliam Wcislo, a behaviorist at the Smithsonian Tropical Research Institute in Panama.

And then there are animals that appear to offload part of their
mental apparatus to structures outside of the neural system entirely.
Female crickets, for example, orient themselves toward the calls of the
loudest males. They pick up the sound using ears on each of the knees of
their two front legs. These ears are connected to one another through a
tracheal tube. Sound waves come in to both ears and then pass through
the tube before interfering with one another in each ear. The system is
set up so that the ear closest to the source of the sound will vibrate
most strongly.

In crickets, the information processing — the job of finding and
identifying the direction that the loudest sound is coming from —
appears to take place in the physical structures of the ears and
tracheal tube, not inside the brain. Once these structures have finished
processing the information, it gets passed to the neural system, which
tells the legs to turn the cricket in the right direction.The Brain Constraint

Extended cognition may partly be an evolutionary response to an
outsized challenge. According to a rule first observed by the Swiss
naturalist Albrecht von Haller in 1762, smaller creatures almost always
devote a larger portion of their body weight to their brains, which
require more calories to fuel than other types of tissue.

Haller’s rule holds across the animal kingdom. It works for mammals
from whales and elephants down to mice; for salamanders; and across the
many species of ants, bees and nematodes. And in this latter range, as
brains demand more and more resources from the tiny creatures that host
them, scientists like Wcislo and his colleague William Eberhard, also at the Smithsonian, think new evolutionary tricks should arise.

In 2007, Eberhardcompared data on the webs built by infant and adult spiders of the same species.
The newborns, roughly a thousand times smaller than the adults in some
cases, should be under much more pressure from Haller’s rule. As a
result, they might be expected to slip up while performing a complex
task. Perhaps the spiderlings would make more mistakes in attaching
threads at the correct angles to build a geometrically precise web,
among other measures. But their webs seemed “as precise as that of their
larger relatives,” Eberhard said. “One of the questions is: How do they
get away with that?”

Japyassú’s work offers a possible solution. Just as octopi appear to
outsource information-processing tasks to their tentacles, or crickets
to their tracheal tubes, perhaps spiders outsource information
processing to objects outside of their bodies — their webs.

To test whether this is truly happening, Japyassú uses a framework suggested by the cognitive scientist David Kaplan.
If spider and web are working together as a larger cognitive system,
the two should be able to affect each other. Changes in the spider’s
cognitive state will alter the web, and changes in the web will likewise
ripple into the spider’s cognitive state.

Consider a spider at the center of its web, waiting. Many
web-builders are near blind, and they interact with the world almost
solely through vibrations. Sitting at the hub of their webs, spiders can
pull on radial threads that lead to various outer sections, thereby
adjusting how sensitive they are to prey that land in those particular
areas.

As is true for a tin can telephone, a tighter string is better at
passing along vibrations. Tensed regions, then, may show where the
spider is paying attention. When insects land in tensed areas of the
webs of the orb spider Cyclosa octotuberculata, a 2010 study found,
the spider is more likely to notice and capture them. And when the
experimenters in the same study tightened the threads artificially, it
seemed to put the spiders on high alert — they rushed toward prey more
quickly.

The same sort of effect works in the opposite direction, too. Let the orb spider Octonoba sybotides go hungry, changing its internal state, and it will tighten its radial threads
so it can tune in to even small prey hitting the web. “She tenses the
threads of the web so that she can filter information that is coming to
her brain,” Japyassú said. “This is almost the same thing as if she was
filtering things in her own brain.”

An orb spider waits on a column made of the gutted corpses of long-ago prey.

Another
example of this sort of interplay between web and spider comes from the
web-building process itself. According to decades of research from
scientists like Eberhard, a spiderweb is easier to build than it looks.
What seems like a baroque process involving thousands of steps actually
requires only a short list of rules of thumb that spiders follow at each
junction. But these rules can be hacked from inside or out.

When experimenters start cutting out pieces of a web as it’s being
built, a spider makes different choices — as if the already-built
portions of silk are reminders, chunks of external memory it needs to
retrieve so it can keep things evenly spaced, Japyassú said. Similarly,
what happens in a web once it is built can change what kind of web the
spider builds next time. If one section of the web catches more prey,
the spider may enlarge that part in the future.

And from the opposite direction, the state of a spider’s nervous
system can famously affect its webs. Going back to the 1940s,
researchers haveexposed spiders to caffeine, amphetamines, LSD and other drugs, attracting
plenty of media attention along the way. Unsurprisingly, these spiders
make addled, irregular webs.

Even skeptics of the extended cognition idea agree that this back and
forth between the web and spider is ripe ground for more investigation
and debate on how to interpret what the spiders are doing to solve
problems. “It introduces a biological setup to the philosophers,” said
Fritz Vollrath, an arachnologist at the University of Oxford. “For that,
I think it’s very valuable. We can start a discussion now.”

But many biologists doubt that this interplay adds up to a bigger
cognitive system. The key issue for critics is a semantic — but crucial —
distinction. Japyassú’s paper defines cognition in terms of acquiring,
manipulating and storing information. That’s a set of criteria that a
web can easily meet. But to many, that seems like a low bar. “I think
we’re fundamentally losing a distinction between information and
knowledge,” Wcislo said. Opponents argue that cognition involves not
just passing along information, but also interpreting it into some sort
of abstract, meaningful representation of the world, which the web — or a
tray of Scrabble tiles — can’t quite manage by itself.

Further, Japyassú’s definition of cognition may even undersell the
level of thought that spiders are capable of, say the spider
behaviorists Fiona Cross and Robert Jackson,
both of the University of Canterbury in New Zealand. Cross and Jackson
study jumping spiders, which don’t have their own webs but will
sometimes vibrate an existing web, luring another spider out to attack.
Their work suggests that jumping spiders do appear to hold on to mental
representations when it comes to planning routes and hunting specific
prey. The spiders even seem to differentiate among “one,” “two” and
“many” when confronted with a quantity of prey items that conflicts with
the number they initially saw, according to a paper released in April.

“How an animal with such a small nervous system can do all this
should keep us awake at night,” Cross and Jackson write in an email.
“Instead of marveling at this remarkable use of representation, it seems
that Japyassú and Laland are looking for an explanation that removes
representation from the equation — in other words, it appears they may
actually be removing cognition.”Evolution in the World

Even leaving aside the problem of what cognition actually is, proving
the simple version of the argument — that spiders outsource problem
solving to their webs as an end run around Haller’s rule — is by itself
an empirical challenge. You would need to show that the analytical power
of the web saves calories a spider would have otherwise spent on the
nervous tissue in a bigger brain, Eberhard said. That would require
quantifying how much energy it takes to build and use a web compared
with the cost of performing the same operations with brain tissue. Such a
study “would be an interesting kind of data to collect,” Eberhard said.

Whether this kind of engineered information-processing happens
elsewhere in nature is likewise unclear. Laland is a high-profile
advocate for the idea of niche construction, a term from evolutionary theory that encompasses burrows, beaver dams and nests of birds and termites.

Proponents argue that when animals build these artificial structures,
natural selection starts to modify the structure and the animal in a
reciprocal loop. For example: A beaver builds a dam, which changes the
environment. The changes in the environment in turn affect which animals
survive. And then the surviving animals further change the environment.
Under this rubric, Japyassú thinks, this back-and-forth action makes
all niche constructors at least candidates to outsource some of their
problem solving to the structures they build, and thus possible
practitioners of extended cognition.Alternatively, more traditional theorists label these structures and
spiderwebs alike as extended phenotypes, a term proposed by Richard
Dawkins. Extended phenotypes are information from an animal’s genes that
they express in the world. For example, bird nests are objects that are
somehow encoded in the avian genome. And as with niche construction,
natural selection affects the structure — different kinds of birds have
evolved to build different kinds of nests, after all. But in the
extended phenotype perspective, that selection ultimately just works
inward, to tweak the controlling information in the animal’s genome.

It’s a subtle difference. But experts who subscribe to Dawkins’s
extended phenotype idea, like Vollrath at Oxford, believe that webs are
more like tools the spider uses. “The web is actually a computer, as it
were,” he said. “It processes information and simplifies it.” In this
view, webs evolved over time like an extension of the spider’s body and
sensory system — not so much its mind. Vollrath’s lab will soon embark
on a project to test just how webs help the spiders solve problems from
the extended phenotype perspective, he said.

While Japyassú, Cheng and others continue to look for extensions of
cognition outward into the world, critics say the only really strong
case is the one with the most metaphysical baggage: us. “It is
conceivable for cognition to be a property of a system with integrated
nonbiological components,” Cross and Jackson write. “That seems to be
where Homo sapiens is headed.”

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About Me

This is a blog about what interests me. Here you will find stories on animals, including animal rights material, cute stuff, and random informative posts about weird, beautiful and interesting creatures. Horses, Spotted Hyenas, and Border Collies will make regular appearances.
Also prominently featured will be posts about the Arts. Animation, photography, and the traditional forms, plus "outsider art," film and books.
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There will be rants. It's an election year, and I am beginning to have a political dimension to my personality. I am also horrified at the level of injustice and violence visited upon people here in the US and elsewhere - particularly against people of color, immigrants, and the LGBT community. Some of these stories will be very hard to read, but I believe we must read them to keep ourselves mindful of the racist and vicious things that happen every day, to speak out when we see discrimination, and root out its evil from ourselves.